Alternating current voltage regulator utilizing electromagnetic switch means, an autotransformer and voltage sensing means



Dec. 31, 1968 D. GUHN ALTERNATING CURRENT VOLTAGE REGULATOR UTILIZINGELECTROMAGNETIC AN AUTOTRANSFORMER AND VOLTAGE SENSING MEANS SWITCHMEANS,

Filed Nov. 7. 1966 INVENTOR DARROLD L. GUHN BY 24W AG EN T United StatesPatent ALTERNATING CURRENT VOLTAGE REGULA- TOR UTILIZING ELECTROMAGNETICSWITCH MEANS, AN AUTQTRANSFORMER AND VOLT- AGE SENSING MEANS Darrold L.Guhn, Logansport, Ind., assignor to Essex Wire Corporation, Fort Wayne,Ind., a corporation of Michigan Filed Nov. 7, 1966, Ser. No. 592,656 3Claims. (Cl. 323-435) This invention relates to alternating currentvoltage regulating systems and more particularly to voltage regulatingsystems including an electromagnetic transformer having winding sectionswhich are selectively connected between input and output voltageterminals by electromagnetic switch means that are automaticallycontrolled by a voltage sensing circuit.

It is often desirable to provide voltage compensating means for certainelectrical loads, such as electronic apparatus, so as to maintain theload voltage within a predetemrined range of values regardless ofvariations in the supply voltage. One object of the present invention isto provide a small, light-weight, low-cost voltage regulator which whenconnected to a source of unregulated alternating current power willoperate automatically to provide a stepped-up output voltage when theinput voltage is below a predetermined low value and to provide asteppeddown output voltage when the input voltage exceeds apredetermined high value.

Another object of this invention is to provide a voltage regulatorsystem wherein the winding sections of a single transformer areselectively connected in step-up and stepdown modes by electromagneticswitch means in response to supply voltage variations above and belownormal values.

Further objects and advantages of the present invention will appear fromthe following description taken with reference to the accompanyingdrawing which is a schematic wiring diagram of a voltage regulatorsystem illustrating the invention.

Referring now to the drawing, there is shown the circult diagram of anautomatic alternating current voltage regulator embodying the invention.The voltage regulator includes a pair of input terminals 10, 11 whichare to be connected to a source of unregulated alternating currentpower. The regulator also includes a pair of output terminals 12, 13 towhich a suitable load may be connected. A conductor 14 connects theinput terminal 11 to the output terminal 13. The remaining terminals and12 are connected by the conductors 15 and 16, respectively, to thecontacts of two power relays or contactors 17 and 18.

The contactor 17 includes an operating coil 19, a pair of normally opencontacts 20, and two pairs of normally closed contacts 21 and 22. Thecontactor 18 includes an operating coil 23, a pair of normally closedcontacts 24, and two pairs of normally open contacts 25 and 26. Themovable contacts of contacts 20 and 22 and the fixed contact of contacts25 are connected to the conductor 15 while the fixed contacts ofcontacts 24 and 26 and the movable contact of the contacts 21 areconnected to the conductor 16. The fixed contact of contacts 20 and themovable contact of contacts 24 are connected by a conductor 32.

The contactors 17 and 18 control the connection of a voltage changing orcompensating transformer 27 to the conductors 15 and 16 to produce asuitable output voltage. While the transformer 27 may have separateprimary and secondary winding sections, it is preferably anautotransformer'having a tapped Winding 28 with end terminals 29 and 30and an intermediate voltage tap 31. The winding 28 of the transformer 27is preferably designed such that the voltage across the winding sectiondefined by end terminals 29 and 30 has a value on the order of ercent ofthat of the voltage of the winding section between the tap 31 and theend terminal 29. The end terminal 29 is connected to the conductor 14and the other end terminal 30 is connected by a conductor 33 to thestationary contact of contacts 21 and the movable contact of contacts25. A conductor 34 connects the tap 31 of the transformer 27 to thefixed contact of contacts 22 and the movable contact of contacts 26.

With the contactor coils 19 and 23 deenergized and the contacts of thecontactors 17 and 18 in the positions shown in the drawing, the sectionof the transformer winding 28 between the terminal 29 and the tap 31will be connected to the input terminals 10 and 11 through the closedcontactor contacts 22. At the same time, the output terminal 12 isconnected through the closed contactor contacts 21 to the end terminal30 of the transformer 27. The transformer 27 thus is connected toincrease or boo-st the voltage across the input terminals 10 and 11 toproduce a higher output voltage across the output terminals 12 and 13.

If the contactor coils 19 and 23 are simultaneously energized to operatetheir respective contacts, the end terminal 30 of the transformerwinding 28 is connected to the input terminal 10 by the contactorcontacts 25 while the output terminal 12 is connected to the tap 31 bythe contactor contacts 26. Thus the voltage produced across the outputterminals 12 and 13 will be lower than that applied to the inputterminals 10 and 11.

The input terminals 10 and 11 may be connected directly to the outputterminals 12 and 13 by energization of the contactor coil 19 while thecontactor coil 23 is deenergized. In this instance, the input terminal10 is connected through the closed contactor contacts 20 and 24 to theoutput terminal 12, so that no voltage change is produced. At the sametime, the transformer terminal 30 and tap 31 are disconnected therebydeenergizing the transformer 27.

To control the energization of the contactors 17 and 18 when the inputvoltage varies, the voltage regulator includes a voltage sensing circuitenergized with a directcurrent potential proportional to the magnitudeof the alternating current voltage across the input terminals 10 and 11.This direct current potential is provided by means of a transformer 35having a primary winding 36 connected to the conductors 14 and 15 and asecondary winding 37 connected to the input terminals 38 and 39 of abridge rectifier 40. The negative output terminal 41 of the rectifier 40is connected to a conductor 42 while the positive output terminal 43 ofthe rectifier 40 is connected to a conductor 44.

The voltage sensing circuit includes a voltage divider network whichcomprises a resistor 45 and a potentiometer 46 connected in seriesacross the conductors 42 and 44. The voltage divider network alsoincludes a second potentiometer 47 which is connected in parallel withthe potentiometer 46 and thus also in series with the resistor 45 acrossthe conductors 42 and 44. A Zener diode 48 has one terminal connected tothe adjustable slider or contact of the potentiometer 46 and has theother terminal connected to the base electrode 49 of a PNP transistor50. The emitter electrode 51 of the transistor 50 is connected to theconductor 44 through a resistor 52 while the collector electrode 53 isconnected to the conductor 42 through the coil 54 of a relay 55 whichhas normally open contacts 56. A capacitor 57 is connected in parallelwith the relay coil 54 to help filter the pulsating voltage output ofthe rectifier 40.

The voltage sensing circuit further includes a second PNP transistor 58having its emitter-collector circuit also connected across theconductors 42 and 44. The emitter electrode 59 is connected through aresistor 60 to the conductor 44 and the collector electrode 61 isconnected to the conductor 42 through the coil 62 of a relay 63 whichhas normally open contacts 64. A filter capacitor 65 likewise isconnected in parallel with the relay coil 62. A second Zener diode 66has one terminal connected to the base electrode 67 of the transistor 58and has the other terminal connected to the adjustable contact of thepotentiometer 47.

As is well known to those skilled in the art, a Zener diode is a siliconjunction device which has the characteristic of preventing reversecurrent flow therethrough when voltages below a predetermined value areapplied across it. When a predetermined voltage is applied to the diode,it breaks down in a reverse direction and permits current flowtherethrough at a value which is essentially limited only the theresistance of the circuit, while the voltage across the diode remainssubstantially constant. When the voltage is reduced below the breakdownvalue, the diode regains its rectifier characteristics of preventingreverse current flow. The voltage sensing circuit of the presentinvention utilizes this characteristic of Zener diodes with the diodes48 and 66 serving as voltage-responsive devices to sense the directcurrent voltage produced at the adjustable contacts of the respectivepotentiometers 46 and 47. The voltages applied to the diodes 48 and 66are each a proportion of the direct current output voltage of therectifier 40 which in turn is a measure of the alternating currentapplied to the regulator input terminals and 11. The Zener diodes 48 and66 are selected to have suitable breakdown voltages so that thepotentiometers 46 and 47 may be adjusted to cause breakdown of the Zenerdiode 48 when the alternating current input voltage exceeds a firstpredetermined value and to cause the breakdown of the Zener diode 66when the alternating current input voltage exceeds a secondpredetermined value greater than the first value.

The contacts 56 of the relay 55 control the energization of the coil 19of the contactor 17 and the contacts 64 of the relay 63 control theenergization of the coil 23 of the contactor 18. The contactor coil 19'has one end connected to the conductor and has its other end connectedto the conductor 14 through the relay contacts 56. Thus the contactorcoil 19 will be energized from the input terminals 10 and 11 wheneverthe relay contacts 56 are closed. Similarly, the coil- 23 of thecontactor 18 is connected in series with the relay contacts 64 acrossthe conductors 14 and 15 to be energized from the input terminals 10 and11 when the relay contacts 64 are closed.

In operation of the voltage regulator at any time that the alternatingcurrent voltage applied to the input terminals 10 and 11 is below afirst predetermined low value, the direct current voltage applied to theZener diodes 48 and 66 will be below the breakdown voltages of thediodes. Therefore the diodes 48 and 66 will prevent flow of the basecurrent in the transistors 50 and 58. Consequently, the transistors 50and 58 will be cutoff and no current will flow through the relay coils54 and 62. The normally open relay contacts 56 and 64 controlled bythese relay coils will prevent energization of the contactor coils 19and 23. Thus the contacts of the contactors 1 7 and 18 will be in theirrespective positions shown in the drawing. The contacts 21 and 22connect the transformer 27 to step-up or increase the supply voltagefrom the input terminals 10 and 11 to a higher output voltage at theoutput terminals 12 and 13.

When the input voltage exceeds a first predetermined low value less thanthat of a second predetermined high value, the Zener diode 48 breaksdown and allows current to flow in the base circuit of the transistor50. This renders the transistor 50 conductive and allows current to flowfrom the conductor 44 through the resistor 52, the emitter-collectorpath of the transistor 50, and the relay coil 54 to the conductor 42.The relay coil 54 is energized by the collector current of thetransistor 50 and causes the relay contacts 56 to close. The closing ofthe relay contacts 56 permits the contactor coil 19 to be energized fromthe conductors 14 and 15 and the contactor 17 accordingly operates toclose its contacts 20 and to open its contacts 21 and 22. The closedcontactor 20 connects the output terminal 12 directly to the inputterminal 10 through the normally closed contacts 24 of the contactor 18.The output voltage of the regulator is therefore identical to the inputvoltage. At the same time, the opening of the contacts 21 and 22 of thecontactor 17 deenergizes the transformer 27.

When the input voltage applied to the terminals 10 and 11 exceeds asecond predetermined high value greater than the first predetermined lowvalue, both Zener diodes 48 and 66 break down. The breakdown of theZener diode 66 renders the transistor 58 conductive. The collectorcurrent of the transistor 58 flows through the relay coil 62 and therelay 63 closes its contacts 64 to energize the coil 23 of the contactor18. As described above, the breakdown of the Zener diode 48 results inthe energization of the coil 19 of the contactor 17. The operatedcontacts of the simultaneously energized contactors 17 and 18 connectthe transformer 27 to step-down or reduce the supply voltage from theinput terminals 10 and 11 to a lower voltage at the output terminals 12and 13.

The voltage sensing circuit is preferably adjusted such that the Zenerdiode 48 will break down only when the voltage across the intputterminals 10 and 11 is greater than a predetermined minimum valuerequired by the load to be connected to the output terminals 12 and 13.It is also desired that the voltage sensing circuit be adjusted suchthat the Zener diode 66 will break down only when the voltage across theinput terminals 10 and 11 exceeds the value which is considered to bethe maximum satisfactory voltage for the load to be connected to theoutput terminals 12 and 13. For use of the regulator with a load havinga nominal voltage rating of 117 volts, the Zener diodes 48 and 66 maybreak down when the voltage appearing between the input terminals 10 and11 exceeds 110 volts and 121 volts, respectively. Assuming that thewinding 28 of the transformer 27 is designed such that the voltageappearing across the end terminals 29 and 30 is 110 percent of thevoltage appearing across the end terminal 29 and the tap 31, it will beseen that the voltage appearing across the output terminals 12 and 13 ofthe regulator will be maintained with the range of 110 to 121 volts asthe input voltage varies from to 133 volts.

What is claimed is:

1. An alternating current voltage regulating system comprising:

first and second input terminals for connection to an alternatingcurrent voltage source having a variable potential;

a first output terminal connected to said first input terminal;

a second output terminal;

a voltage changing transformer having a winding, first and secondwinding terminals defining the ends of a first section of said winding,and a third winding terminal defining one end of a second section ofsaid winding extends from said first winding terminal; said firstwinding section having a greater number of turns than does said secondwinding section;

a first electromagnetic contactor having a first operating coil, anormally closed first switch, a normally closed second switch, and anormally open third switch,

a second electromagnetic contactor having a second operating coil, anormally open fourth switch, a normally open fifth switch and a normallyclosed sixth switch;

voltage sensing circuit connected to said input terminals and responsiveto the potential applied to said input terminals, said voltage sensingcircuit insaid input potential exceeds said predetermined low value;

a second voltage reference means connected between said secondtransistor and said voltage dividing network to control the outputcurrent of said second eluding a first control means connected to saidfirst 5 voltage dividing network to control the output curoperating coilof said first contactor to energize the rent of said second transistorsuch that said second same when the potential applied to said inputtertransistor will be non-conductive until said input minals exceeds apredetermined low value, said voltpotential exceeds said predeterminedhigh value. age sensing circuit including a second control means 3. Thevoltage regulating system according to claim 1 connected to said secondoperating coil of said sec- 10 wherein said voltage sensing circuitcomprises: 0nd contactor to energize the same when the potenrectifiermeans connected to said input terminals and tial applied to said inputterminals exceeds a prehaving an output circuit at which appears adirect determined high value greater than said predetercurrent voltagecontinuously proportional to the almined low value; ternating currentpotential applied to said input terfirst circuit means including saidfirst switch connecting minals;

said third winding terminal of said transformer to a firstelectromagnetic relay constituting said first consaid second inputterminal and second circuit means trol means and having a first coil andnormally open including said second switch connecting said secondcontacts controlling the energization of said first coil windingterminal of said transformer to said second of said first contactor fromsaid input terminals; output terminal so that said transformer isconnected '2! second electromagnetic relay constituting said second in astep-up mode between said input and output control means and having asecond coil and normally terminals when said input potential is belowsaid open contacts controlling the energization of said predeterminedlow value; second coil of said second contactor from said input thirdcircuit means including said third and sixth terminals;

switches in series connection connecting said second first and secondtransistors each having emitter, base input terminal to said secondoutput terminal so that and collector electrodes; said input and outputterminals are directly conmeans connecting the emitter-collector circuitof said nected when said input potential is below said prefirsttransistor and said first relay coil in series across determinedhighvalue and greater than said predesaid rectifier output circuit; terminedlow value; means connecting the emitter-collector circuit of said fourthcircuit means including said fourth switch consecond transistor and saidsecond relay coil in series meeting said second winding terminal of saidtransacross said rectifier output circuit; former to said second inputterminal and fifth circuit a voltage dividing network connected acrosssaid recmeans including said fifth switch connecting said tifier outputcircuit and having first and second interthird Winding terminal of saidtransformer to said mediate voltage takeoff points; second outputterminal so that said transformer is a first Zener diode connectedbetween said first take connected in a step-down mode when said inputpooff point and the base electrode of said first transistor tentialexceeds said predetermined high value. such that said first transistoris conductive only when 2. The voltage regulating system according toclaim 1 said input potential exceeds said predetermined low wherein saidvoltage sensing circuit comprises: value;

rectifier means connected to said input terminals and and a second Zenerdiode connected between said sechaving an output circuit at whichappears a direct 0nd takeoff point and the base electrode of saidcurrent voltage continuously proportional to the alsecond transistorsuch that said second transistor is ternating current potential appliedto said input terconductive only when said input potential exceedsminals; said predetermined high value. a first transistor connected tosaid rectifier output circuit to provide an output current to effectactuation References Cited 0f said fiISt control means; d fi UNITEDSTATES PATENTS a second transistor connected to sai recti er outputcircuit to provide an output current to effect actua- 2168952 8/1939Craig tion of Said Second control means; 2,839,718 6/1958 Luftman et al.323--62 X a voltage dividing network connected across said rectifieroutput circuit;

a first voltage reference means connected between said first transistorand said voltage dividing network to control the output current of saidfirst transistor such that said first transistor will be non-conductiveuntil JOHN F. COUCH, Primary Examiner.

G. GOLDBERG, Assistant Examiner.

U.S. Cl. X.R.

1. AN ALTERNATING CURRENT VOLTAGE REGULATING SYSTEM COMPRISING: FIRSTAND SECOND INPUT TERMINALS FOR CONNECTION TO AN ALTERNATING CURRENTVOLTAGE SOURCE HAVING A VARIABLE POTENTIAL; A FIRST OUTPUT TERMINALCONNECTED TO SAID FIRST INPUT TERMINAL; A SECOND OUTPUT TERMINAL; AVOLTAGE CHANGING TRANSFORMER HAVING A WINDING, FIRST AND SECOND WINDINGTERMINALS DEFINING THE ENDS OF A FIRST SECTION OF SAID WINDING, AND ATHIRD WINDING TERMINAL DEFINING ONE END OF A SECOND SECTION OF SAIDWINDING EXTENDS FROM SAID FIRST WINDING TERMINAL; SAID FIRST WINDINGSECTION HAVING A GREATER NUMBER OF TURNS THAN DOES SAID SECOND WINDINGSECTION; A FIRST ELECTROMAGNETIC CONTACTOR HAVING A FIRST OPERATINGCOIL, A NORMALLY CLOSED FIRST SWITCH, A NORMALLY CLOSED SECOND SWITCH,AND A NORMALLY OPEN THIRD SWITCH, A SECOND ELECTROMAGNETIC CONTACTORHAVING A SECOND OPERATING OIL, A NORMALLY OPEN FOURTH SWITCH, A NORMALLYOPEN FIFTH SWITCH AND A NORMALLY CLOSED SIXTH SWITCH; A VOLTAGE SENSINGCIRCUIT CONNECTED TO SAID INPUT TERMINALS AND RESPONSIVE TO THEPOTENTIAL APPLIED TO SAID INPUT TERMNALS, SAID VOLTAGE SENSING CIRCUITINCLUDING A FIRST CONTROL MEANS CONNECTED TO SAID FIRST OPERATING COILOF SAID FIRST CONTACTOR TO ENERGIZE THE SAME WHEN THE POTENTIAL APPLIEDTO SAID INPUT TERMINALS EXCEEDS A PREDETERMINED LOW VALUE, SAID VOLTAGESENSING CIRCUIT INCLUDING A SECOND CONTROL MEANS CONNECTED TO SAIDSECOND OPERATING COIL OF SAID SECOND CONTACTOR TO ENERGIZE THE SAME WHENTHE POTENTIAL APPLIED TO SAID INPUT TERMINALS EXCEEDS A PREDETERMINEDHIGH VALUE GREATER THAN SAID PREDETERMINED LOW VALUE; FIRST CIRCUITMEANS INCLUDING SAID FIRST SWITCH CONNECTING SAID THIRD WINDING TERMINALOF SAID TRANSFORMER TO SAID SECOND INPUT TERMINAL AND SECOND CIRCUITMEANS INCLUDING SAID SECOND SWITCH CONNECTING SAID SECOND WINDINGTERMINAL OF SAID TRANSFOMER TO SAID SECOND OUTPUT TERMINAL SO THAT SAIDTRANSFORMER IS CONNECTED IN A STEP-UP MODE BETWEEN SAID INPUT AND OUTPUTTERMINALS WHEN SAID INPUT POTENTIAL IS BELOW SAID PREDETERMINED LOWVALUE;